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Traversa A.,University of Bari | Loffredo E.,University of Bari | Gattullo C.E.,University of Bari | Palazzo A.J.,ERDC CRREL | And 2 more authors.
Journal of Soils and Sediments | Year: 2014

Purpose: This study aimed to investigate comparatively the main chemical and physico-chemical properties of the humic acid (HA) fraction of three different composts and to evaluate the bioactive effects of these HAs on the germination and early growth of four populations of switchgrass. Materials and methods: Three compost HAs isolated from a green compost (HAGC), a mixed compost (HAMC), and a coffee compost (HACC) were characterized for some chemical and physico-chemical properties, such as ash content, elemental composition, total acidity, carboxylic and phenolic OH group contents, E4/E6 ratio, Fourier Transform infrared (FT IR), and fluorescence spectroscopies. In subsequent experiments conducted in vitro in a climatic chamber under controlled conditions, the bioactive effects of the three HAs at concentrations of 10, 50, and 200 mg L-1 were tested on the germination and early growth of four switchgrass (Panicum virgatum L.) populations, the octaploids Shelter, Shawnee and Dacotah, and the tetraploid Alamo. Results and discussion: The ash content and the E4/E6 ratio were, respectively, much higher or slightly higher for HACC than for the other two HAs. HAMC showed the lowest C and H contents and the highest O content, whereas HAGC had the highest N content. The total acidity and phenolic OH group content followed the order: HAMC > HACC > HAGC. The fluorescence analysis of the three HAs evidenced a common fluorophore unit possibly associated to simple aromatic structures, such as phenolic-like, hydroxy-substituted benzoic and cinnamic acid derivatives. The FT IR spectra of all HA samples indicated the presence of aromatic phenolic structures. Significant beneficial effects were produced by any HA on switchgrass germination and early growth as a function of the population tested and the HA dose. Conclusions: Results of this study demonstrated that the addition of compost HAs to the germination medium of four switchgrass populations positively influenced the germination process and the growth of primary root and shoot. Significant correlations were found between HA bioactivity and some HA properties. These results suggest a possible use of compost as soil amendment in areas where switchgrass grows naturally or is cultivated. © 2013 Springer-Verlag Berlin Heidelberg.


Shoop S.A.,ERDC CRREL | Hills J.,Antarctic Support Contract | Uberuaga J.,Antarctic Support Contract
Proceedings of the International Conference on Cold Regions Engineering | Year: 2015

The snow roads at McMurdo Station, Antarctica, are the primary transportation corridors for moving personnel and material to and from the airfields servicing intra- and inter-continental air traffic. The majority of the road system is made of snow overlying a snow and ice subsurface. However, at the Scott Base Transition (SBT), the aggregate road leading from Scott Base transitions from the landmass of Ross Island on to the ice shelf and becomes a full depth snow road. Because of the transition between materials, the topography of the area, and extensive use during the austral summer, the SBT is prone to problems unique to that portion of the McMurdo road system and requires specific maintenance activities to remain passable during periods of high temperatures. The SBT area is divided into two subsections. One is the land transition, a soil- or aggregate-surfaced road underlain by permafrost, and the other is the ice transition, a snow-surfaced road underlain by snow and ice. The two sections of the SBT need entirely different construction and maintenance techniques to maintain road surface conditions that will support vehicle traffic. This paper presents some of the issues at the transition area along with maintenance and drainage control measures to alleviate them. © ASCE.


Cole D.M.,ERDC CRREL | Hopkins M.A.,ERDC CRREL | Broadfoot S.W.,ERDC GSL | Sloan S.D.,ERDC GSL
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2013

Although stress wave propagation in granular geologic materials is generally recognized to depend critically on the physical characteristics of the medium, there is a lack of understanding of the physical basis of this process. This knowledge gap inhibits the development of mechanistic models of wave propagation in granular materials and of soil-sensor interaction. To address this important issue, we are currently engaged in an effort to quantify and model the dynamic contact mechanics of granular materials using a combination of micro-scale experimentation, numerical modeling and field validation. We have developed a dynamic contact experimental system that operates at sub-kHz frequencies. This laboratory based system employs piezoelectric crystals to monitor the force transmitted though contacts in a linear array of grains of geologic materials. The deformation over single or multiple contacts is measured, allowing the constitutive behavior of the contacts to be quantified. The paper describes this system in a configuration for normal loading, and presents initial results for a large-grained quartz sand. Our approach to developing detailed contact laws (that account for both elastic and inelastic deformation) is described. The implementation of material-specific contact laws in a discrete element model is also described with a focus on small normal displacements. The DEM simulates wave propagation as a function of measurable grain-scale properties and includes the simulation of polyellipsoidal and polyhedral particle shapes and Hertzian and non-Hertzian laws for contact stiffness and frictional loss. In addition, the paper describes a number of research interests that are supported by this work. © The Society for Experimental Mechanics, Inc. 2013.


Ryerson C.C.,ERDC CRREL | Tripp S.T.,USCG RandD Center
Society of Petroleum Engineers - Arctic Technology Conference 2014 | Year: 2014

Superstructure icing occurs when spray freezes on offshore platforms and ships. Though superstructure ice accumulates fastest on moving vessels that generate bow spray, stationary structures also ice in storms. And ice from atmospheric sources also accumulates, affecting parts of platforms and ships not affected by sea spray. Icing is often accepted as an inconvenience to offshore operators, but that tolerance can reduce safety, operational tempo, and productivity. This report shows how to evaluate the impact of superstructure and atmospheric ice to offshore platform and ship functions and components from work conducted for the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE), and for the US Coast Guard using questionnaires and observations. The report proposes a risk matrix approach for assessing the relative threat of ice from sea spray, frost, snow, rime and glaze to the safety and functions of platforms and ships, and demonstrates how to identify and prioritize areas requiring ice protection. It also briefly describes available ice protection techniques other than baseball bats and mallets. The goal is to provide a resource for offshore operators with superstructure icing-related safety concerns.Copyright 2014 Offshore Technology Conference.


Kevern J.T.,University of Missouri - Kansas City | Zufelt J.E.,ERDC CRREL
ISCORD 2013: Planning for Sustainable Cold Regions - Proceedings of the 10th International Symposium on Cold Regions Development | Year: 2013

Over the past 20-30 years, permeable pavement installations have become wide-spread for stormwater control, especially in urban areas. A large amount of design guidance for permeable pavements exists in the literature; however, much of the guidance uses experience and case studies from warm regions. Permeable pavements have been successfully utilized in cold climates for stormwater management and often have ancillary benefits, such as reduced potential for slip and fall. ASCE's Technical Council on Cold Regions Engineering (TCCRE) has assembled the Permeable Pavements in Cold Climates monograph to address issues specific for freeze-thaw climates. The new for 2013 monograph brings together current industry best practices for designing, constructing, and maintaining permeable pavements with considerations specific to cold climates. This paper will provide an overview of the monograph and important areas of design, construction, and maintenance for pervious concrete, porous asphalt, and interlocking permeable pavements. © 2013 American Society of Civil Engineers.


Wagner A.M.,ERDC CRREL | Yarmak Jr. E.,Arctic Inc
ISCORD 2013: Planning for Sustainable Cold Regions - Proceedings of the 10th International Symposium on Cold Regions Development | Year: 2013

Migration of aqueous phase contaminants from underground tanks, nuclear waste sites, and in situ waste treatment areas into the groundwater is of concern at many locations. There is a wide range of technologies to remediate contaminated sites. Some examples are: constructed wetlands, air sparging, bioremediation, and permeable reactive barriers. One technology that has not been widely used is frozen soil barriers. The barrier provides containment of liquid contaminants in order to prevent their migration to adjacent areas. This is a promising method that is environmentally friendly and offers a safe alternative to other methods. Frozen barriers can be formed using a series of subsurface freezing pipes or probes. The installation of frozen barriers disturbs the existing ground minimally and only existing in-situ material is used. An artificial frozen barrier using hybrid thermosyphons was installed in Fairbanks, Alaska using six thermosyphons placed at a distance of 1.5 m. The system ran actively for about 60 days and operated in a passive phase during the winter months. A detailed description of the thermal performance of the barrier in Fairbanks from March through September will be presented. © 2013 American Society of Civil Engineers.


Arntsen A.E.,Dartmouth College | Song A.J.,ERDC CRREL | Perovich D.K.,Dartmouth College | Richter-Menge J.A.,Dartmouth College
Geophysical Research Letters | Year: 2015

The Arctic sea ice cover evolves dramatically through the summer melt season. Floe size distribution (FSD) is a critical parameter used to examine this change as the ice cover transitions from large rectilinear plates in spring to an ensemble of discrete rounded floes by midsummer. The FSD at a given time impacts the dynamic and thermodynamic behavior of the ice cover. Focusing on the seasonal marginal ice zone in the Beaufort and Chukchi Seas from May to September 2014, we present qualitative and quantitative results derived from National Technical Means high-resolution imagery and supported by ice mass balance buoy data. Results indicate that as melt accelerates, floe breaking pattern, and therefore FSD, is heavily influenced by the distribution of melt ponds. Discrete element model results using morphological conditions derived from analyzed satellite imagery confirmed that breaking occurs along ponds and perpendicular to applied stress. Key Points Floe size distribution in the marginal ice zone is heavily impacted by summer thermodynamics A network of mature melt ponds acts as linked perforations facilitating floe breakup in summer In the MIZ, FSD changes by the removal of thin floes due to surface and bottom melting © 2015. The Authors.


Perovich D.K.,Dartmouth College | Richter-Menge J.A.,ERDC CRREL
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2015

In recent years, the Arctic sea ice cover has undergone a precipitous decline in summer extent. The sea ice mass balance integrates heat and provides insight on atmospheric and oceanic forcing. The amount of surface melt and bottom melt that occurs during the summer melt season was measured at 41 sites over the time period 1957 to 2014. There are large regional and temporal variations in both surface and bottom melting. Combined surface and bottom melt ranged from 16 to 294 cm, with a mean of 101 cm. The mean ice equivalent surface melt was 48 cm and the mean bottom melt was 53 cm. On average, surface melting decreases moving northward from the Beaufort Sea towards the North Pole; however interannual differences in atmospheric forcing can overwhelm the influence of latitude. Substantial increases in bottom melting are a major contributor to ice losses in the Beaufort Sea, due to decreases in ice concentration. In the central Arctic, surface and bottom melting demonstrate interannual variability, but show no strong temporal trends from 2000 to 2014. This suggests that under current conditions, summer melting in the central Arctic is not large enough to completely remove the sea ice cover. © 2015 The Author(s) Published by the Royal Society. All rights reserved.


Affleck R.T.,ERDC CRREL | Carr M.,ERDC CRREL
Proceedings of the International Conference on Cold Regions Engineering | Year: 2015

McMurdo Station watershed in Antarctica is one of the southernmost basins that annually experiences active water flow during the austral summer. This runoff, primarily from snowmelt, has daily and seasonal fluctuations. The flow fluctuation and variation depend on the air temperature and on many other factors. At times, extreme runoff has occurred at McMurdo Station such that water overflows across the roads and bypasses the culverts, creating disruption and massive erosion. Knowing when the peak runoff occurs is critical for operation and maintenance of the channels. We conducted an analysis of indicators relating the air temperature and cloud cover to flow rate to quantify when significant flow occurred. Flow data taken during austral summers 2009-2010 and 2010-2011 were used in the analysis. Based on the correlation between the change in accumulated thawing degree-days and cloudiness expressed as clearness, the time delay in the peak discharge can occur between 4 and 14 days after a peak temperature. Relating temporal indicators and flow records, a relationship between real time data and the need for maintenance personnel to implement mitigation factors could be achieved. © ASCE.


Hohenegger C.,University of Utah | Alali B.,University of Utah | Steffen K.R.,University of Utah | Perovich D.K.,ERDC CRREL | And 2 more authors.
Cryosphere | Year: 2012

During the Arctic melt season, the sea ice surface undergoes a remarkable transformation from vast expanses of snow covered ice to complex mosaics of ice and melt ponds. Sea ice albedo, a key parameter in climate modeling, is determined by the complex evolution of melt pond configurations. In fact, ice-albedo feedback has played a major role in the recent declines of the summer Arctic sea ice pack. However, understanding melt pond evolution remains a significant challenge to improving climate projections. By analyzing area-perimeter data from hundreds of thousands of melt ponds, we find here an unexpected separation of scales, where pond fractal dimension D transitions from 1 to 2 around a critical length scale of 100 m2 in area. Pond complexity increases rapidly through the transition as smaller ponds coalesce to form large connected regions, and reaches a maximum for ponds larger than 1000 m 2, whose boundaries resemble space-filling curves, with D 2. These universal features of Arctic melt pond evolution are similar to phase transitions in statistical physics. The results impact sea ice albedo, the transmitted radiation fields under melting sea ice, the heat balance of sea ice and the upper ocean, and biological productivity such as under ice phytoplankton blooms. © 2013 Author(s).

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